1. Field of the Invention
This invention relates to a digital movement recording apparatus which is carried by a vehicle and records movement data representative of a moving condition of the vehicle as digital data.
2. Description of the Prior Art
Digital movement recording apparatus are conventionally known which employ, as a record medium, a memory card adapted to be removably inserted into a recording section of a vehicle. In such memory card, movement data including a speed, a travel distance and so forth for each movement are recorded in a specific format. Such specific format is illustratively shown in FIG. 7. Referring to FIG. 7, a conventional memory card of such specific format has a first record area (movement data record area) 2a and a second record area (ID record area) 2b. In the first record area 2a, movement data UD.sub.1 to UD.sub.n representative of particulars of movements of a vehicle are recorded together with time data STD.sub.1 to STD.sub.n and ETD.sub.1 to ETD.sub.n representative of starting and ending times of such movements. Meanwhile, in the second record area 2b, address data AD.sub.1 to AD.sub.n representative of addresses of the first record area 2a at which the ending time data ETD.sub.1 to ETD.sub.n are recorded, respectively, are recorded.
Since such digital movement recording apparatus records movement data for each movement of the vehicle as described above, it includes means for detecting starting and ending of a movement of the vehicle. Such starting and ending of a movement of the vehicle are normally detected either by detecting switching on and off, respectively, of an ignition switch or an accessory switch or by detecting insertion of a memory card into a recording section to prepare for recording and removal of the memory card from the recording section to disable recording, respectively. Thus, if it is detected that the ignition switch is switched on or a memory card is inserted into the recording section, then it is determined that a movement of the vehicle is started and the time then is written into the first record area 2a of the memory card as starting time data ST representative a starting time of the movement. Subsequently to such recording of the starting time, movement data UD including a speed during the movement and distance data are successively written into the first record area 2a of the memory card. After then, if it is detected that the ignition switch is switched off or the memory card is removed from the recording section, it is determined that the movement comes to an end and the time then is written as ending time data ETD representative of an ending time of the movement into the first record area 2a of the memory card subsequent to the movement data UD. Then, ending address data AD representative of an address of the first record area 2a of the memory card at which the ending time data ETD are recorded are written into the second or ID record area 2b of the memory card. Thus, with such ending address data AD, the movement data from the starting time to the ending time can be recognized as movement data during the movement of the vehicle.
While a memory card has, in addition to a movement data record area, an ID record area for recording ending address data therein in order to allow a movement of a vehicle from a starting time to an ending time to be recognized as movement data of a movement as described above, such ID record area is limited in storage capacity. Accordingly, if the ignition switch or accessory switch is switched on and off by a great number of times or if a memory card serving as a record medium is inserted and removed by a great number of times, then all of the storage capacity of the ID record area may be used up. In this instance, while the movement data record area still remain empty sufficiently and can record data therein, movement data each including a starting time, a speed and distance data and an ending time cannot be recorded into the memory card any more. Further, where each of a starting time and an ending time requires, for example, 6 bytes for year, month, day, hour, minute and second, each updating of the ID record area involves reduction by of a remaining portion of the movement data record area by 12 bytes. Accordingly, the memory card must be exchanged for a new memory card after a short interval of time, which is uneconomical.